Treating and preventing painful fractures could be improved by strengthening cortical bone – the hard outer shell of all bones in the skeleton. We don’t know how cortical bone forms, but if we did, we could improve its strength. We have found that a brain-like network of cells inside the skeleton, called osteocytes, use a specific signal, called SOCS3, to make strong cortical bone. This study will find out how SOCS3 works and find new ways to make cortical bone strong and healthy.